In the application of compositions to traveling substrates, it is common to generate a foam that carries the composition and to apply the foamed composition from an applicator nozzle across the width of a traveling substrate. As the foam disintegrates on and into the substrate, the bulk of the composition remains on or in the substrate without being washed or carried away, as is the case when compositions are applied in a liquid carrier by padding or emersion in a bath. Thus, the application of foamed compositions minimizes the waste of excess composition and the generation of hazardous or otherwise harmful waste water or other carrier waste.
An example of a foam application is the treatment of a traveling textile substrate with dye, size, softeners, resins and other agents.
Usually, when it is intended that the applied composition impregnate the substrate, the applicator applies the foam composition under pressure and at a location where the substrate is free or unsupported on the side of the substrate opposite the foam applicator. Substrates that are generally dimensionally stable, such as woven textiles, can be treated in this manner. However, substrates that have a tendency to be dimensionally unstable, such as knitted textiles, non-wovens, elastic fabric, and other somewhat uncontrollable substrates, have not been capable of having foamed compositions applied over an uncontrolled path of the substrate between supports because of the tendency of such substrates to contract widthwise and/or to have edges curl inwardly in the unsupported extent of the path of travel.